1. Field
The present invention relates to an anode shroud for an electrolytic oxide reduction system.
2. Description of Related Art
An electrochemical process may be used to recover metals from an impure feed and/or to extract metals from a metal-oxide. A conventional process typically involves dissolving a metal-oxide in an electrolyte followed by electrolytic decomposition or selective electrotransport to reduce the metal-oxide to its corresponding metal. Conventional electrochemical processes for reducing metal-oxides to their corresponding metallic state may employ a single step or multiple-step approach.
A multiple-step approach is typically used when a metal-oxide has a relatively low solubility in the electrolyte. The multiple-step approach may be a two-step process that utilizes two separate vessels. For example, the extraction of uranium from the uranium oxide of spent nuclear fuels includes an initial step of reducing the uranium oxide with lithium dissolved in a molten LiCl electrolyte so as to produce uranium and Li2O in a first vessel, wherein the Li2O remains dissolved in the molten LiCl electrolyte. The process then involves a subsequent step of electrowinning in a second vessel, wherein the dissolved Li2O in the molten LiCl is electrolytically decomposed to regenerate lithium. Consequently, the resulting uranium may be extracted, while the molten LiCl with the regenerated lithium may be recycled for use in the reduction step of another batch.
However, a multi-step approach involves a number of engineering complexities, such as issues pertaining to the transfer of molten salt and reductant at high temperatures from one vessel to another. Furthermore, the reduction of oxides in molten salts may be thermodynamically constrained depending on the electrolyte-reductant system. In particular, this thermodynamic constraint will limit the amount of oxides that can be reduced in a given batch. As a result, more frequent transfers of molten electrolyte and reductant will be needed to meet production requirements.
On the other hand, a single-step approach generally involves immersing a metal oxide in a compatible molten electrolyte together with a cathode and anode. By charging the anode and cathode, the metal oxide can be reduced to its corresponding metal through electrolytic conversion and ion exchange through the molten electrolyte. However, although a conventional single-step approach may be less complex than a multi-step approach, the metal yield is still relatively low. Furthermore, reducing a metal oxide to its corresponding metal will result in the production of oxygen gas, which is corrosive and, thus, detrimental to the system if not properly addressed.